A woman in Califonia who received a lung transplant from a young man got more than she bargained for when she developed his peanut allergy.
The 68-year-old had her left lung replaced with the donor's organ in 2017 because she had emphysema, a condition which causes permanent damage.
She was recovering well until, one day before she was due to go home, she began struggling to breathe and felt tightness in her chest in a 'severe reaction'.
Initially baffled, doctors made the link to a food allergy when she told them the symptoms began immediately after eating a peanut butter and jam sandwich.
Although she had never had a nut allergy before, medics checked with the transplant agency and discovered the donor was allergic and had passed it on.
The phenomenon is 'very rare', experts said, but has been documented multiple times before with nuts, fish, milk, eggs and wheat.
Further tests revealed the unnamed woman, in San Diego, California, had also become allergic to almonds, cashews, coconuts and hazelnuts.
The lead author of the study and doctor who treated the patient at the medical centre at the University of California, San Diego, Dr Mazen Odish, said he only knew of four or five cases of this happening.
A new lung had been given to the woman because her own was so damaged by emphysema, in which the small air sacs in the lung break down.
Emphysema is usually caused by tobacco smoking and cannot be cured, but gradually worsens over time, making it increasingly difficult to breathe.
The female patient is believed to have inherited the 22-year-old man's allergy when cells from his organ entered her body.
Allergic reactions happen when immune cells overreact, thinking something such as a nut or pollen is a danger to the body.
During the transplant, cells from the man's body – which trigger reactions in the presence of nuts – were passed on and now have the same effect in the woman.
Doctors advised her to avoid all peanuts and tree nuts and gave her an EpiPen in case she had another attack, LiveScience reported.
They are not sure whether the allergy will last for the rest of her life, or if her own immune system will overpower it and return to normal in future.
Other cases of allergies being passed on have occurred in liver, kidney, lung, bone marrow, heart and kidney transplants.
The phenomenon has been found to be more likely in children and people taking the drug tacrolimus, which suppresses the patient's immune system to stop their body rejecting the organ – the patient in this case was taking the medication.